Doctor mechanism for rolls and cylinders



vJuly 26, 1949. E. R. LJuNGQulsT 2,477,339

DOCTOR MECHANISM FOR ROLLS AND CYLINDERS Filed Feb. 14, 1945 Inventor: Emf ljunjqusl' by @WW Ht Iamey Patented July 26, 1949 2,477,339 DOCTOR MECHANISM FOR ROLLS AND CYLINDERS Ernst R. Ljungquist, Worcester, Mass., assignor to Lodding Engineering Corporation, Worcester, Mass., a corporation of Massachusetts Application February 14, 1945, Serial No. 577,890

2 Claims. (Cl. 92-74) The present invention relates to devices known in 'the paper making art as doctors or scrapers, such devices being customarily employed in connection with rotating calendar rolls, drier cylinders, and the like, for the purpose of cleaning the .surfaces of such rolls and cylinders, or removing a web of paper therefrom, as in the manufacture of crepe paper. In Lodding Patent No. 2,117,032 issued May 10, 1938, there is shown and describe a doctor mechanism of the above indicated type, characterized by the provision of a thin flexible doctor blade carried by a relatively sti holder that is pivotally mounted to turn about an axis parallel to the axis of the rotating surface being doctored. In operation, the holder of the Lodding patented doctor is adapted to `apply pressure to the blade in a direction opposite to reactions set up along the edges of the blade by the surface being doctored and by the rigid holder, through operation of a member of greater stillness than the blade for engaging the blade surface intermediate such edges.

The object of the present invention is to provide certain improvements in the above described patented construction, as regards the manner of supporting and applying pressure to the blade, so that the blade can bend longitudinally throughout its width and thereby adjust itself to the moving surface being doctored. Brley stated, the present invention contemplates the provision of an improved holder for the doctor blade.` so constructed that while the blade is applied, as a whole, to the roll by turning of the holder. auxiliary pressure can be applied in varying amounts to localized areas of the free or back edge of the blade to cause the blade to t itself closely to the surface being doctored. Such blade adjustment is particularly advantageous when using the blade as a. creping doctor to remove a web of paper completely from the Vroll surface.

The above and other advantageous features of the invention will hereinafter more fully appear from the following description, with reference to the accompanying drawing, in which:

Fig. 1 is a transverse sectional view of a doctor mechanism embodying the present invention.

Fig. 2 is a plan view of the mechanism shown in Fig. 1.

Fig. 3 is a sectional view similar to Fig. 1, illustrating the manner of adjusting the free or back edge of the doctor blade.

Fig. 4 is a sectional view illustrating a modified form of blade holder embodyingthe invention.

Referring to the drawings, a portion of the sur- 2 face of a roll or cylinder is indicated at I, and a holder 2 embodying the invention is carried by an arm 3 turnable about a pivot 4 with respect to the roll I. Suitable means, not shown, are provided for imparting a turning movement to the arm 3 about its pivot 4, thus tending to swing the holder 2 in the direction of the arrow to bring one edge of a doctor blade 5 carried by the holder 2 into engagement with the moving surface of the roll I. The blade 5 is composed of any suitable thin flexible material, such as steel, brass, or a synthetic composition, such as Bakelite.

The holder 2 consists of a bar 6 secured to the pivoted arm 3 by means of a clamp 1 and bolts 8, and the outer end of the bar `6 provides a notch 9 in which is received the rear edge of the blade 5. The holder 2 also comprises a member II) secured to the bar 6 by screws II, and the member III alsoprovides a seat I2 in which is received a portion of a pressure plate I3. `The pressure plate I3 extends beyond the edge of the holder to engage the blade 5 between its edges, with the thickness of the pressure plate I3 being such that it is relatively stiff, as compared to the doctor blade 5.

Consequently when the blade 5 is applied to the roll surface i by turning movement imparted to the arm 3 about its pivotal axis, as indicated by the arrow, the free end of the plate I3 engages the blade 5 between its edges to cause the blade to assume the position of Fig. l, wherein the blade is inclined with respect to the plate I3. That is to say, the free or back edge of the blade 5 tends to move away from the pressure plate I3 towards the upper side ofthe notch 9. This yielding of the blade 5 in response to pressure applied to the plate i3, in a direction opposite to the reactions set up along its scraping edge and its back edge as seated in the notch 9, re-

sults in an effective application of the blade. as`

awhole, to the surface being doctored. c i

As previously pointed out', the doctor blad mounting of the present invention is particularly adapted for use in connection with creping doctors, and in the illustrative embodiment of the invention shown in Fig. 1, the blade 5 is being utilized for the production of crepe paper, with the scraping edge of the blade serving to remove a paper web W from the surface of the roll I with a. creping action. In the operation of such a creping doctor, it is of the utmost importance that the blade maintain rm contact with the roll surface, notwithstanding `irregularities of the roll and resulting local deformations of the doctor blade, so that the paper web will be removed evenly from the roll surface. Therefore. the present invention contemplates the provision of means. adjustable independently of the blade holder itself, for causing the blade to iiex at ditferent points along its length to insure uniform engagement of its scraping edge with the roll surface.

To this end, the holder 2 further provides a number of fingers I4 mounted on top of the bar 8 by means oi' studs I5. It is to be noted in Fig. 1 that the opening I5 in each finger I4 through which the stud I passes is slightly larger than the stud, so that the iinger I4 is capable oi' limited pivoted movement about the stud I5. The end of each finger I4 extending toward the roll overhangs the edge of the bar l. and provides a bent portion Il adapted to engage the doctor blade 5 closely adjacent to where it emerges from the notch 9. The opposite end of the finger I4 extends over a seat I8 provided by the bar 6, and with the blade 5 occupying the position of Fig. 1, the pressure exerted on the blade by the plate I3 is normally suillc'ient to hold the finger I4 in an upwardly inclined position, with theleft hand end of the iinger I4 tending to bottom in the seat I8. The exact relation of each finger Il with respect to its seat I 8 is determined by an adjusting screw I9 in threaded relation with respect to the bar 6, andturnable to bring its upper end into engagement with the end of a finger I 4 adjacent to the seat I8.

Assuming that the blade 5 has been applied to the roll I by turning of the arm 3 about its pivot l, it is evident that the paper web W will be removed from the roll l with a creping action, as indicated. While the pressure applied to the blade 5 by the plate I3 is normally suflicient to cause the blade to perform satisfactorily upon a perfectly cylindrical roll surface, it has been found that irregularities of the roll surface will tend to deform the blade locally, thereby preventing unifrom contact of its scraping edge with the roll surface. According to the present invention, the undesirable results of any such abnormalities in operation are overcome by individually operating the fingers I4 through their screws I9 to exert localized pressure on the back edge of the doctor blade, opposite to the pressure exerted bythe plate I3 in applying the blade to the roll.

The operation of a finger I4, in so applying localized pressure to the blade 5, is illustrated on an exaggerated scale in Fig. 3, wherein the screw I8 has been turned to engage the under side of the linger I4 and force it away from its seat |18. As a result, the finger I4 tends to swing about its .loose mounting on the stud I5 to cause its bentover end II to engage the free back edge of the blade adjacent the notch 9. Thus the particular portion of the blade engaged by the finger I I is flexed sufficiently so as to unseat it from the notch 9, while adjacent portions of the blade remain seated, as indicated. The net result of such localized flexure of the blade, as opposed to its normal flexure by the pressure plate I3 results in applying that portion of the scraping edge opposite to the zone of deflection by the finger Il more closely to the roll surface I.

Therefore the several fingers Il and their adjusting screws I9 provide readily operable means for causing the doctor blade 5 to firmly contact the roll I at all points along the scraping edge of the tableI irrespective of irregularities of the roll surface, or the existence of any other factors tending to interfere with the uniform scraping action of the blade 5 along its whole length. .As a result. the operator of a machine equipped with an improved doctor blade mounting of the present invention can, by selective manipulation of the adjusting screws I9, overcome any abnormalities of operation, by causing just the right amounts of secondary iiexure of the blade independently of the primary pressure which serves to press the blade, as a whole, upon the roll.

Referring now to Fig. 4, there is shown the mounting of a doctor blade 5a in accordance with the present invention to perform a doctoring action on that portion of a roll surface I a that is located above the roll axis, so that the blade 5a performs a cleaning action, as compared to the removal of a web by the creplng doctor 5 shown in Fig. l, which engages the roll below its axis of rotation. In this modified form of mounting, the pivotal arm 3 carries a one-piece holder 20 having a longitudinal slot 2| providing off-set seats 22 and 23. 'Ihe doctor blade 5a is normally maintained in engagement with the lower seat 22 Iby a pressure plate 24 engaging the blade intermediate its edges, with the plate 24 -providing ears 24a to maintain the blade 5a in the slot 2|.

In order to provide for localized 'bending of the blade 5a adjacent its back edge, a number of fingers 25 are loosely supported by studs 26 from the under side of the holder 20. An adjusting screw 21 threaded into the holder is adapted to engage the inner end of each finger 25 and turn it about its stud 26, so as to engage the back edge of the blade 5a and flex it away from the seat 22. The screws 21 can also be utilized to maintain the pressure plate 24 in the slot 2|, by freely passing through openings in the plate.

From the foregoing it is apparent that by the present invention` there is provided an improved mounting for a doctor blade, characterized by the provision of means for obtaining localized iiexure of the blade adjacent its free or back edge, to cause the working edge of the blade to firmly engage the moving surface being doctored under conditions of operation such as might otherwise result in an uneven doctoring action. By reason appreciable wear of the scraping of the fact that the auxiliary pressure fingers are adapted to operate on the back edge of the blade, they will perform their function irrespective of the width of the blade. Therefore any edge will not upset the action of the fingers, since the screws I9 and 2l give a wide range of adjustment in the pressures applied thereby.

I claim:

l. A doctor mechanism for rolls and cylinders comprising in combination, a pivotally mounted Aholder providing a first and a second seat disposed lengthwise of the front end portion thereof, a flexible blade of a thickness substantially less than the depth of said first seat and having one edge portion freely received within said first seat, a plate of greater stiffness than said blade and having one edge portion mounted in said second seat with its opposite edge portion extending beyond said first seat and intermediate its edges thereby to apply the other edge of said blade to a rotating surface in response to movement of said holder about its pivot, accompanied by a primary fiexure of said blade, a series of fingers pivotally mounted at intervals along said holder, with the ends of said fingers bearing on said blade at different points adjacent the front edge portion of said first seat, and adjusting screws threaded into said holder i'or engaging the opposite ends of said iingers engaging said blade 2. A doctor mechanism for rolls and cylinders comprising in combination, a pivotally mounted holder providing a rst and a second seat disposed lengthwise ot the front end portion thereof, a plane imperforate flexible blade of a thickness substantially less than the depth of said nrst seat and having one edge -portion freely received within said ilrst seat, a plate of greater stiffness than said blade and having one edge portion rigidly mounted in said second seat with its opposite edge portion extending beyond said iirst seat and engaging said blade intermediate its edges thereby to apply the other edge of said blade to a rotating surface in response to movement of said holder about its pivot, accompanied by a primary fiexure of said blade, a series o! iingers pivotally mounted at intervals along said holder with the ends of said fingers bearing on said blade at diiIerent points between the front edge of the first seat and said plate, and adjusting screws threaded into said holder for engaging the opposite ends of said ngers thereby selectively to impart a secondary iiexure to said blade with respect to said first seat in accordance with the individual adjustment of said screws, with said secondary iiexure of the blade by said fingers being in a direction opposite to that in which the blade is flexed through its application to the surface being doctored by said plate.

ERNST R. LJUNGQUIST.

REFERENCES 'CITED The following referenlces are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,119,816 Fogarty Dec. 8, 1914 1,552,363 Vickery Sept. 1, 1925 1,803,927 Vedder May 5, 1931 1,907,623 Vickery May 9, 1933 1,912,605 Vickery June 6, 1933 1,927,694 Wood Sept. 19, 1933 2,117,032 Lodding May 10, 1938 2,287,350 Lodding June 23, 1942 2,376,502 Overton May 22, 1945 

